RE: [squid-users] Sporadic high CPU usage, no traffic

 
>
> I'm at a loss. Here's the situation. We have a couple hundred squid
> clients forced (using never-direct allow all) to run through
> a parent proxy
> array. On occasion (no discernable pattern) the squid process on the
> clients uses all the available CPU cycles, and tailing the
> access log shows
> that nothing is being served. Attempting to use the
> cachemgr.cgi (from a
> different box) or the squidclient (on the client proxy)
> returns no results
> while the CPU usage is running wild. Once the CPU usage
> slows down, results
> are returned. Running a squid -k debug (for the usual 2 seconds) and
> tailing the cache.log seems to show acls being processed. Often in
> conjunction with these CPU spikes I'll see "TCP connection to
> [parent-proxy]
> failed", but not always. Sometimes these connection failed
> messages appear
> in the cache log without a CPU spike.
>
> There are two round-robin parent proxies, which peer (using
> ICP) and a third
> "master" parent (also peering with ICP) which is running two
> squid processes
> (one per CPU) due to some sites not handling "sessions"
> changing IPs. All
> three are on the same network switch. They are being
> monitored with MRTG
> (http://mrtg.schoolaccess.net/squid/) and never seem to slow down.
>
> The connection failed messages don't favor one server over the other.
>
> Most of the clients are accessing the internet over
> satellite, but some are
> on terrestrial links. The problem does not occur more often
> with either
> connection method.
>
> I thought that I had found the problem when I read about the
> half_closed_clients bug, but after patching, compiling and installing
> SQUID2.5-STABLE7 on a couple of sites, the problem persists
> (though perhaps
> less often). Disabling half-closed-clients in the squid.conf,
> unsurprisingly had no noticeable effect.
>
> The version I replaced for testing is SQUID2.5-STABLE4.
>
> STABLE7 was compiled with --bindir=/home/squid2/bin
> --sbindir=/home/squid2/bin --libexecdir=/home/squid2/bin
> --datadir=/home/squid2/etc --sysconfdir=/etc/squid
> --localstatedir=/home/squid2 --mandir=/usr/man --enable-ssl
> --enable-err-languages=English --disable-ident-lookups --with-pthreads
> --enable-storeio=ufs,aufs,diskd --enable-snmp
> --enable-async-io --with-aio
>
> STABLE4 was compiled with --bindir=/home/squid2/bin
> --sbindir=/home/squid2/bin --libexecdir=/home/squid2/bin
> --datadir=/home/squid2/etc --sysconfdir=/etc/squid
> --localstatedir=/home/squid2 --mandir=/usr/man
> --enable-xmalloc-statistics
> --enable-useragent-log --enable-referer-log
> --enable-err-languages=English
> --disable-ident-lookups --with-pthreads
> --enable-storeio=ufs,aufs,diskd
>
> In the interest of preventing this message from becoming too
> long, I have
> posted the conf files at http://mrtg.schoolaccess.net/squidconf/. The
> -sparse files have all comments and blank lines stripped out.
>
> What further tools can I use (on a Linux 2.2 kernel) to
> figure out what
> squid is doing when the CPU usage spikes? What information
> did I leave out
> that might be relevant?

  You may issue :

  % squid -k debug ; sleep 2 ; squid -k debug

  during this high CPU usage. Check cache.log afterwards.

  M.
  
Received on Thu Oct 28 2004 - 23:46:12 MDT